It has been stated that a heightened sense of smell occurs during PMS and due to stress. Is this true?

Last night I came back and noticed the smell of watermelon before I opened the fridge. Then today, one of my roommates was eating watermelon and I didn't smell it at all until one of them said that watermelon has no smell. Now I can't smell it again. Then I read on this website that sense of smell increases before a woman's monthly cycle, and that it can also happen due to stress. Is that true?